1. Field of the Invention
The field of art to which this invention pertains is the preparation of catalyst for the hydrotreatment of hydrocarbon-containing feeds. The invention relates to a process for the preparation of a presulfided catalyst, a process for the preparation of a sulfided catalyst, and the use of said sulfided catalyst in the catalytic hydrotreatment of hydrocarbon-containing feeds.
2. Prior Art
In the oil industry many processes are known in which hydrocarbon-containing feeds are catalytically treated with hydrogen, such as hydrodesulfurization, hydrodenitrogenation, and hydrocracking. In such processes use is made of catalysts built up from a carrier material, such as alumina, on which there are deposited one or more catalytically active metals or compounds thereof; examples of such metals are molybdenum, nickel, cobalt and tungsten.
It is common knowledge that optimum results are obtained in using such catalysts when the catalytically active metals are in their sulfided form. See for instance H. Hallie's article in Oil & Gas Journal, Dec. 20, 1982, Technology, pp. 69-74, which also describes several techniques for preparing sulfided catalysts. These techniques comprise treating a fresh catalyst in a reactor at elevated temperature with a combination of hydrogen sulfide and hydrogen, a naturally sulfurous feed (non-spiked feed), or a feed to which a sulfur compound, such as carbon disulfide or dimethyldisulfide, has been added (spiked feed).
Although these techniques are practiced on a large scale, they nevertheless display several drawbacks. For instance, they require accurate control to achieve the desired result and are time-consuming, and the sulfur compounds used cause odor nuisance. Moreover, protracted interruption of the actual hydrotreatment of the hydrocarbons is needed if, as is often the case in actual practice, the reactor in which these processes are carried out is used for sulfiding catalysts.
To meet these drawbacks it is proposed in European patent application No. 0,153,233 that the fresh catalyst or a regenerated one should be contacted ex situ, i.e. outside the reactor in which the actual hydrotreatment of hydrocarbon-containing feeds is carried out, with an aqueous solution of diammonium sulfide, and the resulting material be dried to obtain a presulfided catalyst, whereupon the resulting presulfided catalyst is activated in situ or not in the presence of hydrogen, i.e. is brought into the sulfided state. This proposal also has its drawbacks, however. Firstly, aqueous diammonium sulfide is a reagent which produces an extremely objectionable odor. Secondly, if the total amount of the catalytically active metal is to be brought into the sulfided form, then, according to the teachings of the patent specification, the presulfiding should comprise at least two impregnating steps with the aqueous diammonium sulfide; in this process each impregnating step should be followed by a drying step, and the final drying step should preferably be carried out in an inert atmosphere, such as nitrogen. A disadvantage to such a preparative process is its laboriousness when used in actual industrial practice. Thirdly, it has been found that the drying during the preparation of catalysts according to said patent specification is attended with the release of hydrogen sulfide, causing environmental problems. Finally, it has been found that these catalysts display an objectionably poor activity.
U.S. Pat. No. 3,477,963 (Van Venrooy) describes the sulfiding of hydrotreating catalyst. Van Venrooy requires first transforming an organic sulfur compound into a mixture of gases (by passing it over a presulfided catalyst) comprising H.sub.2 S, CH.sub.4, CH.sub.3 --SH and CH.sub.3 --S--CH.sub.3. It is this mixture of gases that is contacted with the unsulfided catalyst in a second step or stage.
U.S. Pat. No. 4,814,315 (Kukes et al.); 4,020,012 (Miura et al.) and 3,959,179 (Mikovski et al.) are typical of prior art references which require calcining of presulfided catalysts in air prior to any contact of the catalyst with a reducing atmosphere. This results in the finished catalyst containing little if any of the catalytically active metals being in their sulfided form. As mentioned above, optimum results for use of such catalysts will be realized only when the catalysts are in their sulfided form.
U.S. Pat. No. 4,320,030 (Happel et al.) describes making particles of active metal salts obtained from a solution of such salts in molten ammonium thiocyanate or thiourea (no carrier material is employed). Water is removed from the solution and the mixture heated to decompose the organic sulfur compounds and the mixture heated to decompose the organic sulfur compounds and evolve gases including sulfur dioxide and yield a black solid mass. Eventually, particles of this mass are heated in a reducing atmosphere. This reference teaches that the organic sulfur compound is a precursor for hydrogen sulfide.
U.S. Pat. No. 4,845,068 (Takahashi et al.) describes the use of organic thiol-group-containing organic acids to presulfide hydrotreating catalysts which are then activated with hydrogen gas at elevated temperature.